The invention pertains to an apparatus for testing the watertight capacity of pipe sections, for example, waste water discharge pipes, especially pipes connecting houses to mains. The apparatus employs pipe sealing pads and utilizes a process for determining the location of a leak in a pipe section. As prescribed by German Industry Norm DIN 4033, each connection and each pipe in a public waste water discharge system has to be subjected to a test to determine that it does not leak. It is accordingly subjected to water pressure of 0.5 bar (11/2 times atmospheric) pressure. In order to test sections of pipes to which unrestricted access can be gained at both ends, pipe sealing pads, for example, those identified in DE-OS 27 48 614 or in German Design Patent No. 84 13 877 are employed.
The pipe sealing pads have a cylindrical sleeve and two circular walls at each end, or have the shape of a cushion composed of two concentric cylinders or sleeves between which a medium, generally air, can be introduced and which requires only a radial, circular-shaped wall. Cushions of this latter type frequently are mug-shaped, the sealing wall being sited at one end of the circular shaped, expandable unit. When pipes, for example, waste-water discharge pipes, are being tested as to leakage, it is normal to seal each end of the connection with a pipe sealing pad, the end being sealed off by inflation. At least one of the sealing pads has a tube by means of which this space between the two sealing pads can be filled or emptied. Observation of the static pressure in the space between the two pads will reveal whether a leak exists or not, since a drop in pressure signals the presence of a leak.
This testing process, however, cannot be employed if the section of pipe is accessible from only one end. This is especially the case with household connections. Normally there is also a main connector located under the street having connections of various diameters and shapes. The connection from each household, usually a circular pipe of 150 mm diameter, (which diameter with curving and extension is increased to 250 mm at the main collecting point) is attached to the main collector. An inspection shaft (square or circular in shape and, if circular, with a diameter of 80 cm.) is normally located, dependent on the level of the street, 10 to 16 feet (3 to 5 meters) deep. Free access to the household connection can be gained only from this inspection shaft, for which reason testing can be carried out only from one end. As at the present time there exist no testing devices for such an inspection it has been usual up to now to refrain from testing household connections.
The present operation is intended to remove this deficiency. Its purpose is to provide a device for testing whether sections of pipe which can be accessed or tested from one side only are free from leaks. It is especially intended that household connections should be capable of being tested from the inspection shaft without the main pipe having to be accessible. This task is solved by an apparatus for testing whether sections of pipe (for example, pipes for waste-water discharge, especially household connections) have sprung a leak. The apparatus has two pipe sealing pads. To the back wall of the front sealing pad is attached both a hose for emptying and filling and a connection for a distancing rod which can be pushed forward and pulled backward. The rear pipe sealing pad is a ring-shaped seal though which the pipe, tubing for releasing air and tubing for filing the space between the two sealing pads are conducted. This rear sealing pad can also be connected to the distancing rod. In addition, it has attached through to the inner area tubing for emptying and filing the space formed between the two pipe sealing pads.
The apparatus is operated in the following manner. The front pipe sealing pad is first inserted from the accessible end into the pipe to be tested. The purpose of the distancing rod is to advance the front pipe sealing pad along the section of pipe to be tested until it reaches the required position. This position can be determined by the length of the distancing rod which has been inserted or by a feeler attached to the front face of the sealing pad. Then the second or the rear, sealing pad is inserted into the piping. If the front sealing pad is inflated with air by means of the hose and the rear sealing pad is filled by means of its tubing, the two sealing pads will press all around on the inside wall of the pipe to be tested, thereby creating between them an area which can be tested. The distancing rod keeps the two pipe sealing pads the desired distance apart and absorbs such axial pressures as are produced during the subsequent testing procedure. The area between the two pipe sealing pads can now be filled with water by means of the pertinent tubing, the air between the two pads being allowed to escape via the air discharge tubing. This tubing by means of which the air is allowed to escape should ideally contain a float so that at all times the air can be drained away from even the highest point of the cross section of the pipe. When not air but water is discharged via this air discharge tubing one can ensure that the area betweent he two pipe sealing pads is filled with water.
The testing pressure of 11/2 times atmospheric pressure or whatever pressure is desired is now generated and, after the flow of water to the section to be tested has been shut down, the pressure over the section which has been sealed off is observed to determine how it changes. For this purpose a manometer is attached to the tubing by means of which the area sealed off is filled. If the pressure slowly decreases, it can be assumed there is a leak in the section of piping under test. If the pressure remains constant there is no leak. Ideally, the sensor which is attached to the front face of the front pipe sealing pad should be an adjustable rod which has a sphere attached to its front end. The sphere prevents the sensor from becoming stuck in a separating device in the pipe or on small corners when the front sealing pad is inserted by means of the distancing rod into the pipe to be tested. Because the rod attached to the sensor is adjustable in length it is possible to position the front sealing pad at a predetermined location from a given, particular point. For example, when a household connection is to be tested, the length of the sensing rod is set to the diameter of the main collecting pipe into which the household pipe flows. In its preferred embodiment, the apparatus contains a special feature in that there is a seal. This permits the distancing rod to be moved axially so that even in the sealed state, that is, when the rear pipe sealing pad is expanded and thus locked in position, the position of the front sealing pad can be varied. In this way it will be possible to move the front sealing pad backwards and forwards without having to vary the position of the rear sealing pad. The position of leaks in the pipe under scrutiny can thereby be ascertained. The apparatus solves the additional task of providing a process for determining the location of a leak in pipes to which there is access from only one end, for the apparatus described above provides for testing whether or not a leak is present. In this process the rear sealing pad is expanded and thereby locked in position while the position of the front sealing pad is varied by pushing or pulling the distancing rod as required. For each test the front sealing pad is expanded at the new position so that it seals off its end of the piping, whereupon the section of piping thus sealed off by the two cushions is tested as to leaks. If indeed there is a leak in a longer section of pipe this can be verified by firstly a test over the whole length. A leak manifests itself in a loss of pressure. If a second segment has the axial position of the front sealing pad altered, and the process is repeated, then eventually it can be determined that the location of the leak is beyond the position of the front sealing pad, that is to say, outside the limits defined by the two sealing pads. This will be evident when there is no drop in pressure over the length of pipe being tested. In this way the location of each leak can be determined with very great accuracy, for example, to within 10 cm.
Further advantages and characteristics of the invention derive from the appended claims as well as from the following description, it being understood that the examples referred to are not intended to represent an exhaustive list. The examples are discussed with reference to the drawing.